Apparatus for measuring friction force between a magnetic head and a magnetic disk

Abstract

An apparatus for measuring a maximum static friction force is disclosed, in which the displacement of the relative positions of first and second objects due to the operation of a driving unit is suppressed for measuring an accurate static friction force characteristic. The static friction force measuring apparatus for measuring the static friction characteristic between a first object fixed on a mounting base and a second object in contact with the first object and held in a holder comprises an external force buffer interposed between the mounting base and the mounting base side fixed end of the apparatus, a speed controller arranged in the drive unit for controlling the relative speeds of the holder and the mounting base to a level sufficiently low as compared with the resonance frequency of a frictional force detector, and a device for suppressing the displacement of the relative positions of the first and second objects to such an extent that the external force exerted substantially in parallel with the contact surface between the two objects exceeds the maximum static friction force. The frictional force detector detects the maximum static friction force immediately before the displacement begins between the two objects.

What is claimed is: 
     
       1. A static friction force measuring apparatus for measuring the static friction characteristic between a first object and a second object in contact with the first object, comprising: a mounting base having said first object fixed at an end thereof and the other end thereof secured to a first fixed end of said apparatus;   a holder having an end thereof holding said second object and the other end thereof secured to a second fixed end of the apparatus;   a frictional force detector, arranged at an arbitrary position between said holder-side fixed end and said mounting base side fixed end other than the portion where said first end and second objects are in contact with each other, for measuring a maximum static friction force immediately before the displacement begins between said two objects;   drive means for applying an external force to a selected one of (a) between said holder and said holder-side fixed end and (b) between said mounting base and said mounting base side fixed end of the apparatus in a direction substantially parallel with the contact surface between said two objects;   an external force buffer for suppressing the displacement between the relative positions of said two objects to the extent that the external force, exerted substantially in parallel with the contact surface of the two objects, exceeds the maximum static friction force, said buffer being arranged between said mounting base and said mounting base side fixed end of the apparatus; and   a speed controller mounted on said drive means for controlling the relative speeds of said holder and said mounting base to a level sufficiently low as compared with the resonance frequency of said frictional force detector.   
     
     
       2. A static friction force measuring apparatus according to claim 1, wherein: said first object is a magnetic disk, said second object is a magnetic head, said mounting base is a spindle carrying said magnetic disk, said drive means is a motor having a rotative axis coaxial with the rotational axis of said spindle, and said elastic member is directly coupled between the rotative axis of said spindle and the rotative axis of said motor.   
     
     
       3. A static friction force measuring apparatus according to claim 1, wherein: said first object is a magnetic disk, said second object is a magnetic head, said mounting base is a spindle carrying said magnetic disk, said drive means includes a motor having a rotative axis not coaxial with the rotational axis of said spindle and a roller mounted on the rotative axis of said motor and having an outer peripheral portion thereof frictionally engaging an outer peripheral portion of said spindle, and said elastic member is directly coupled between the rotative axis of said roller and the rotative axis of said motor.   
     
     
       4. A static friction force measuring apparatus according to claim 1, wherein: said first object is a magnetic disk, said second object is a magnetic head, said mounting base is a spindle carrying the magnetic disk, said drive means is a motor having the rotational axis thereof coaxial with the rotative axis of said spindle, and said external force buffer includes a rod and a spring, said rod having a fulcrum at the holder-side fixed end, a point of application at the the point where said rod is connected with said friction force detector and a point of action between said fulcrum and said point of application, said spring having an end thereof mounted on said point of action of said rod and the other end thereof secured to a portion other than said holder-side fixed end.   
     
     
       5. A static friction force measuring apparatus according to claim 1, wherein: said first object is a magnetic disk, said second object is a magnetic head, said mounting base is a spindle carrying said magnetic disk, said drive means is a motor having a rotative axis thereof coaxial with the rotative axis of said spindle, and said external force buffer includes a rod and a spring, said rod having a fulcrum at the holder-side fixed end, a point of application at the point where said rod is connected with said friction force detector and a point of action on the side opposite to the point of application with respect to said fulcrum, said spring having an end thereof mounted on said point of action of said rod and the other end thereof fixed at a position other than said holder-side fixed end of the apparatus.   
     
     
       6. A static friction force measuring apparatus according to claim 1, wherein: said first object is a magnetic disk, said second object is a magnetic head, said mounting base is a spindle carrying said magnetic disk, said drive means is a piezoelectric device interposed between said frictional force detector and said holder-side fixed end, and said elastic member is directly coupled between the rotative axis of said spindle and said mounting base side fixed end of the apparatus.   
     
     
       7. A static friction force measuring apparatus according to claim 1, wherein: said first object is a magnetic disk, said second object is a magnetic head, said mounting base is a spindle carrying said magnetic disk, said drive means is a piezoelectric device interposed between said frictional force detector and said holder-side fixed end, and said external force buffer includes a roller having a rotative axis not coaxial with the rotative axis of said spindle and said elastic member directly coupled between the rotative axis of said roller and the mounting side fixed end of the apparatus.   
     
     
       8. A static friction force measuring apparatus according to claim 1, wherein: said first object is a magnetic disk, said second object is a magnetic head, said external force buffer is arranged between said holder-side fixed end and said holder, and said drive means includes an external force buffer made of said elastic member and a piezoelectric device arranged at said holder-side fixed end.   
     
     
       9. A static friction force measuring apparatus according to claim 1, wherein: said first object is a magnetic disk, said second object is a magnetic head, said mounting base is a spindle having a bearing, said frictional force detector is arranged between said holder and said holder side fixed end, and said drive means is arranged above or under said mounting base in a spaced apart and opposed relationship therewith, a magnet is arranged on at least one of said mounting base and said drive means, the other of said mounting base and said drive means has a magnet arranged thereon or formed of a magnetic material, and said external force buffer is means for generating a selected one of a magnetic attractive force and a magnetic repulsive force between said drive means and said mounting base.   
     
     
       10. A static friction force measuring apparatus for measuring the static friction characteristic between a first object and a second object in contact with the first object, comprising: a mounting base having said first object fixed at an end thereof and the other end thereof secured to a first fixed end of said apparatus;   a holder having an end thereof holding said second object and the other end thereof secured to a second fixed end of the apparatus;   a frictional force detector arranged at an arbitrary position between said holder-side fixed end and said mounting base side fixed end other than the portion where said first end and second objects are in contact with each other for measuring a maximum static friction force immediately before the displacement begins between said two objects;   drive means for applying an external force to a selected one of (a) between said holder and said holder-side fixed end and (b) between said mounting base and said mounting base side fixed end of the apparatus in a direction substantially parallel with the contact surface between said two objects;   an external force buffer including suppressing the displacement between the relative positions of said two objects to the extent that the external force, exerted substantially in parallel with the contact surface of the two objects, exceeds the maximum static friction force, said external force buffer being arranged between said holder-side fixed end and said holder; and   a speed controller mounted on said drive means for controlling the relative speeds of said holder and said mounting base to a level sufficiently low as compared with the resonance frequency of said frictional force detector.   
     
     
       11. A static friction force measuring apparatus according to claim 1, wherein said external force buffer is an elastic member taking a shape of one of a rectangular parallel-piped and a spiral. 
     
     
       12. A static friction force measuring apparatus according to claim 10, wherein said external force buffer is an elastic member taking a shape of one of a rectangular parallel-piped and a spiral.